Daily Hygroscopic Inertia Classes: Application in a Design Method for the Prevention of Mould Growth in Buildings

Abstract

The persistence of high relative humidity values inside buildings favours mould growth on material surfaces, causing their degradation and bringing about social and economical problems for the users. Heating and ventilating are fundamental actions for the control of humidity in the indoor environment, but the hygroscopic inertia provided by the materials that contact the inside air can be a complement for that control. As the hygroscopic inertia concept can be very difficult to approach for building designers, a definition of daily hygroscopic inertia classes is presented, based on numerical and laboratory work on this subject. An outline of a simple method, using those classes, that allows for the evaluation of the reduction of mould growth potential associated to a configuration of inside finishes is proposed. The method is then used in several hygrothermal scenarios to illustrate how different values of hygroscopic inertia can contribute to the prevention of mould growth in buildings. The analysed scenarios also contribute to a sensitivity analysis of the influence in relative humidity of several parameters such as outside climate, ventilation, vapour production, heating, solar gains and envelope quality combined with hygroscopic inertia.